In a bogie of a railcar, an axle box accommodating a bearing supporting a wheelset is supported by an axle box suspension so as to be displaceable relative to a bogie frame. There are various types of axle box suspensions. Among them, an axle beam type axle box suspension is configured such that: an axle spring constituted by a coil spring is interposed between the axle box and a side sill of the bogie frame located above the axle box; and a tip end portion of an axle beam extending from the axle box along a car longitudinal direction is supported so as to be displaceable relative to a receiving seat projecting downward from the bogie frame (see PTL 1, for example).
As shown in FIG. 12 as a specific example, in a conventional axle beam type axle box suspension 1, a core rod 5 is attached to a tubular portion 3 through an elastic bushing (axle beam supporting rubber) 4, the tubular portion 3 being located at a tip end of an axle beam 2 extending from an axle box (not shown) in a car longitudinal direction (paper surface leftward/rightward direction). A protruding portion 5d formed at each car width direction (paper surface vertical direction) side surface of the core rod 5 is fitted from below into a fitting groove 7a of a receiving seat 7 projecting downward from a side sill 6a of a bogie frame 6. Then, a lid member 8 is provided on a lower surface of the receiving seat 7 so as to support the protruding portion 5d from below and close a lower end opening of the fitting groove 7a and is fixed to the receiving seat 7 using two first bolts B1 and B2.